Flexible and elastic tanks for transporting liquids in bulk

ABSTRACT

1,035,957. Carrying liquid cargo. GAZOCEAN S.A., and PNEUMATIQUES CAOUTCHOUC MANUFACTURE ET PLASTIQUES KLEBER COLOMBES. Oct. 10, 1963 [Oct. 10, 1962], No. 40020/63. Headings B7A and B7S. [Also in Division F4] A ship&#39;s hull 30, Fig. 3 (not shown), having insulation 31, has a main tank 33 therein for containing liquid surrounded by a second tank 36, each tank being formed from a non-metallic membrane of a flexible and elastic material, e.g. nitrile rubber or polyester urethane. The space 37 between the tanks is filled with a pressurized gas, a flexible cellular material or a liquid. Alternatively, the upper part of the space may be filled with cellular material and the separated lower part by a pressurized gas. The space 37 may also be divided into several sealed chambers by membranes which extend between the tanks, each chamber being filled with gas at different pressures. Inflatable reinforcing ribs (Fig. 2, not shown) filled with an inert gas may be arranged on the internal surface of the main and/or the second tank.

J. H. ALLEAUME l-:TAL 3,272,373

FLEXIBLE AND ELASTIC TANKS FOR TRANSPORTING LIQUIDS IN BULK Filed Oct.lO,

FIG]

www

INVENTORS JEAN H. ALLEUME ENIS HAMEL ATTORNEY sept. 13, 196s UnitedStates Patent O 3,272,373 FLEXIBLE AND ELASTIC TANKS FOR TRANS- PORTINGLIQUDS 1N BULK Jean Henri Alleaume, 121 Ave. du Marechal Foch, Saint-Cloud, Seine, France, and Denis Marcel Henri Hamel,

4 Ave. Victor Hugo, Saint-Mande, Seine, France Filed Oct. 10, 1963, Ser.No. 315,329 Claims priority, application France, Oct. 10, 1962, 911,88112 Claims. (Cl. 220-9) The present invention relates to flexible tankmeans adapted to rest on the hull of a `ship for transporting liquid.This arrangement is particularly suitable for transporting coldliquefied gases at a pressure close to atmospheric pressure by sea orriver.

As is known, in ships of this kind, the walls of the tank do not undergo hydrostatic and hydrodynamic stresses, which are fully transmitted tothe hull of the ship and supported by it.

However, the walls of the tanks which may undergo considerablevariations of temperature and whose dimensions and geometrical shaperemain more or less constant, since they are rigidly connected to thehull of the ship which supports them, must be designed to supportdimensional variations which are often considerable, without abnormalstresses.

Different solutions, whose object is to confer qualities on the walls ofthe tank permitting them to resist these dimensional variations, withoutsustaining damage, have already been suggested. Thus it has beenproposed to make tanks whose walls are made up either of a weldedassembly of corrugated metal plates or of flat plates connected togetherby means of flexible bellows elements which are also metal; in each ofthese cases, the metal Walls are made integral with an insulating layer.It has also been proposed to fix a film of a synthetic material to theinsulating layer, this film having the required qualities ofimpermeability and chemical inertness.

The structures made in this way exhibit thermal expansions yorcontractions which are not exactly compensated at all points. This isthe case particularly when the walls are made up of a film fixed to theinsulating layer, but also when they are metal plates.

Further, in certain cases-for instance, in the case of a heavy swell ora collision-they may sustain severe damage which may even render them nolonger airtight since they must, by their very design, follow all thedeformations of the hull of the ship and have virtually no mechanicalresistance.

In the case of tanks with metal walls, the production of the usuallyfairly complicated shapes which are necessary has the furtherdisadvantage of entailing an operation which is often fairly delicateand, moreover, likely to render the metal less resistant to thermalfatigue; in any case, it may be considered relatively expensive.

Moreover, the checking, and, where necessary, the repair of the tank andthe insulating layer are long and expensive operations which oftennecessitate the removal and sometimes even the destruction of certainparts.

Finally, in all cases, the positioning of the walls of the tanks (filmsor metal plates) is an operation which cannot be carried outindependently of the construction of the ship, Whose going into servicemust therefore be prolonged by the time necessary for the operation ofpositioning the walls of the tanks.

Tanks have also been proposed which are made up of a membrane forming astructure independent of the remainder of the ship on which it restsdirectly or indirectly, without however being rigidly fixed to it.

In the drawings:

FIGURE 1 shows a cross-section through a prior art ICC tank made up of amembrane forming an independent structure.

FIGURE 2 shows a perspective view of a ltank which is used as firsttank;

FIGURES 3, 4, 5 respectively show cross sections through variouscombinations of ship hulls in accordance with the invention. Y

In the structure shown in FIGURE 1, the ships hull, schematically shownat 10, has an inner coating of a thermally insulating layer 11, theliquid to be transported being presumedas frequently occursto be at alow temperature. The liquid is contained in the tank 12 made of amembrane 13 which is kept in place, by any appropriate fixing means,schematically illustrated at 14, to the lips of the orifice 15 used forfilling and emptying the tank. Thus the tank is formed by a sort of bagheld at the neck and taking up, when full, all the available spaceenclosed by the insulating layer. The membrane 13 is then applied to theinsulating layer 11 which transmits the hydrostatic and hydrodynamicstresses to the hull. The membrane 13 must have the usual qualities ofirnpermeability and chemical inertness relating to the product to betransported. It must also be sufficiently flexible at its workingtemperature to be able to alter its shape so that the parts in contactwith the liquid transported remain constantly applied to the layer 11 towhatever extent the tank is filled and whatever the movement of the shipmay be. It must also have sufficient elasticity to sustain withoutdamage the thermal stresses it undergoes.

It has only been proposed to make such tanks of a composite material,for example a glass fiber cloth which is coated with a plasticchemically inert to liquid. These tanks have only a Wall.

The heterogeneity of the material makes difficult the construction ofsuch tanks by welding and the elasticity and the flexibility of coatedglass fiber cloth are insufficient to transmit -completely hydrodynamicand hydrostatic stresses and to sustain the thermal stresses.

It is also necessary, as an additional security measure, to duplicatesuch a tank by a second so-called secondary barrier tank, so that thereexists at every point at least two fluid tight walls between theliquified gas `and the rigid structure of the ship. This secondarybarrier is made up of metallic sheets placed inside the thermallyinsulating layer.

In the present invention, these Adifliculties are successfully avoided.

Our tank is made up of a homogeneous, flexible and elastic material andhas two Walls so that there exists at every point at least twofluid-tight walls between the liquified gas and the rigid structure ofthe ship.

The first tank which contains the liquid is duplicated by the secondtank made of the same material or of an analogous homogeneous material.

The second tank is in contact with the first tank or it is separatedfrom the first tank. The second tank can bebound to the first tank bydifferent means or it can be independent of .the first tank.

Several elastomers may be used, e.g. nitrile rubbers, polyurethanes, andsimilar elastomers. A polyester urethane such Ias that sold under thetrademark Estane has been found particularly suitable because of itsimpermeability, its resistance to hydrocarbons, its flexibility, itselasticity, its mechanical resistance and its resistance to wear, all ofthese being qualities Which it keeps at low temperatures. Tanksaccording to the present invention may be made of sheets of a suitableelastomer, such as that known under the trademark Estane,5 such sheetsbeing relatively thin, e.g. 1 to 4 mm. joined together by high frequencylwelding, by hot-air welding or by any other appropriate means.

It will be appreciated that the invention is not limited to tanks whosewalls are made of a specific elastomer. Any homogeneous material havingthe required qualities of impermeability and chemical inertness whichmaintans, at the temperature at which the liquid is transported,sufficient exibility and elasticity, is suitable.

The tanks according to the invention can be subjected to thermal fatiguedue to the considerable variations in temperature they undergo, with norisk of them tearing, as a result of homogeneity and the elasticity oftheir wall at the working temperature. They transmit the hydrostatic andhydrodynamic forces to the hull better than previously known tanks. Thesecurity is increased as a result of the two walls between the liquidand the structure of the ship.

IFurthermore -it is unnecessary to place a distinct secondary -barrierwhich entails considerable shortening of the construct-ion period of theship. lFor periodic checks, and where necessary, repairs, these tankslmay easily lbe fully or partially withdrawn from the cell in which theyare placed.

Finally, tanks according to the invention facilitates the successive orsimultaneous transport of chemically or physically incompatiblecargoes-the products to be transported may easily be placed in separateor different tanks.

In an embodiment which is not illustrated, the first tank and the secondtank are independent and are directly in contact. The top o-f the firsttank is applied on the top of the hold by a plurality of straps and thesuperior part of the second tank (Which is the secondary barrier) isfastened to the walls of the hold.

FIGURE 2 shows a particular embodiment of a first tank. '1`o preventabnormal strain on the neck of the tank, inflatable ribs 21 are arrangedon the inner wall thereof. Their object is to maintain the shape of thetank 'when the Ilatter is empty or only partially filled. To elim-Iinate `any risk of explosion in the case of leakages, they are inflatedwith an inert gas such as nitrogen.

In the embodiment illustrated in FIGURE 3, the hull 30 and also' thelower surface of the deck are covered by a thermally insulating layer31.

The walls of the tank 32 are made up of a membrane 33, which, as in thepreceding example, forms a sort of bag held by its neck with anappropriate fixture schematically illustrated at 34, to the lips of thefilling and emptying orifice 35.

A secondary tank whose walls 36 are applied directly to the layer 31completely surrounds the tank 32. It is designed and made like the tank32 from which it is separated by a layer 37 of an inert gas kept at apressure approximately equal to the pressure at the bottom of the tank32, at least during the period the tank 32 contains liquid. It will beappreciated that the walls 36 and 33 are hermetically connected togetherat the top, and there are means, which are not shown in the figure, andwhich do not per se form part of the invention, which make it possibleto insert the compressed gas in the gap between the walls 36 and 33.

The pressure of the gas of the layer 37 applies the walls 36 of thesecondary tank against the thermally insulating layer 31 and keeps themain tank 32 separated from the secondary tank. The gaseous layer 37isthermally insulating, which makes it possible to reduce considerablythe thickness of the layer 31.

The walls 36 of the secondary tank form a safety secondary barrier,which, should there be a break in the seal of the main tank 32,insulates the rigid struct-ure 30 from the cold liquid. As a result ofits flexibility and its elasticity, the wall 36 could sustain withoutdamage the stresses it would undergo if the cold liquid trans-ported inthe bank 32 came into contact with it by accident.

This arrangement also makes it possible to protect the Walls 33 and 36from any stress resulting from a change of shape of the hull and toobviate any friction between them and the layer 31.

According to one modification, the layer 37 is made up of a'liquidhaving appropriate chemical and physical characteristics. The layer 37may also be made of a fiexible cellular material.

According to another modification of the invention, the gap between thewall 36 and the wall 33 is maintained at several points by means ofmembranes connecting the wall 33 and the Wall 36 around their Wholeperimeter. Thus a certain number of sealed chambers are defined, each ofwhich may be supplied With a pressure different from that of the otherchambers and which is to be adapted to the pressure of that part of theWall 33 which corresponds to the particular chamber.

A particular embodiment of this modification is shown in FIGURE 4.

The Walls 43 and 46 are analogous to the walls 33 and 36 in theembodiment shown in FIGURE 3. A membrane 48 is fixed to each of them inthe neighborhood of their lower edges and, running around the entireperimeter, dedines two sealed chambers 47a and 'll-7b. :Each of thesechambers is supplied with a different pressure. The pressure of thechamber 47 b may be at least equal to the pressure exerted on the bottomof `the tank containing the liquid and the pressure of the -chamber 47amay be the pressure necessary for keeping the tank formed by the wall 43in place. In this particular case, the carrying function of the tank(carried out by the chamber 47h) is dissociated from the centeringfunction (carried out by the Achamber 47a).

In the embodiment shown in FIGURE 5, the main and secondary tanks arearranged as in the embodiments illustrated in FIGURES 3 and 4. Thereferences 53 and 56 designated the walls lof these tanks. They areanalogous to the walls 33 and 36, 43 and 46 in the preceding examples.

The gap between these walls is filled at its upper part 57s with aflexible cellular matrial, and may, if required, be hermetically sealed,and at its lower part 57i by an inert gas which is kept under pressure.Should the seal of the cellular material which fills the gap 57s beinsufficient, iit is possible, for example, to separate the two parts57s and 57i from one lanother by a membrane 59 fixed around the entireperimeter onto the Wall 53 and the wall 56.

As in the preceding example, it is also possible to separate the gap 57iby means of a membrane fixed to the wall 53 and the wall 56 along theiredges and thus to define two chambers which may be supplied withdifferent pressures.

Where the principal tank is surrounded by a secondary tank, it ispossible to arrange ribs inflated with an inert gas on the internalsurface of each or merely on the internal surface of one of them.

It will be appreciated that the invention is not limited to theforegoing embodiments, and that modifications may be made to thespecific details set forth.

What is claimed is:

1. A device for the transport of liquids in bulk comprising an outerwall, a thermally insulating layer disposed adjacent the inner surfaceof said outer wall and a double- Walled container disposed within saidthermally insulating layer, said double-walled container consisting ofspaced main and second tanks, each of said tanks bei-ng made of ahomogeneous and intrinsically flexible and elastic material.

2. Device for the transport of liquids as claimed in claim 1 whereinsaid tanks consist of a non-reinforced membrane made of the samehomogeneous and intrinsically flexible and elastic material.

3. Device for the transport of liquids as claimed in claim 1 wherein atleast one of said tanks consists of a non-reinforced membrane made of apolyester urethane.

4. Device for the transport of liquids as claimed in claim 1 wherein thespace between said main tank and said second tank is filled with a gaswhich is kept under pressure.

5. Device for the transport of liquids as claimed in claim 1 wherein thespace between `said main -tank and said second tank is filled with `aflexible cellular material.

6. Device for the transport -of liquids as claimed in claim 1 whereinthe space between said main tank and said second tank is lled with aliquid.

7. Device for the transport of liquids as claimed in claim 1 wherein thespace between said main tank and said second tank is yfilled at itsupper part with a ex-ible cellular material and at its lower part with agas which is kept under pressure.

8. Device for the transport of liquids as claimed in claim 1 whereinsaid main tank and said second tank are connected with one another by atleast one membrane dividing up the space separating said tanks intosealed chambers.

9. Device for the transport of liquids as claimed in claim 1 whereinsaid thermally insulating layer envelops all sides of said second tank.

10. Device for the transport of liquids as claimed in claim 8 whereineach sealed chamber is filled with a gas kept under pressure at apressure which is different for each chamber.

11. Device for the transport of liquids as claimed in claim 8 wherein atleast one of said sealed chambers is lled with a flexible cellularmaterial and at least one of References Cited by the Examiner UNITEDSTATES PATENTS 611,207 9/ 1898 Morrill 15G-2.1 2,387,258 10/ 1945 Hague.2,477,787 8/ 1949 Cook 229-14 2,484,608 10/1949 Cheyney 229-14 2,751,9536/1956 Grimm. 2,991,906 7/ 1961 Eligoulachvili 114-74 2,994,452 8/1961Morrison 220-9 3,058,624 10/ 1962 Westlake 222-107 3,067,712 12/ 1962Doerpinghaus 114-74 3,164,186 1/1965 Weber et al. 150-3 JOSEPH R.LECLAIR, Primary Examiner.

FRANKLIN T. GARRETT, Examiner.

J. F. MCNULTY, Assistant Examiner.

1. A DEVICE FOR THE TRANSPORT OF LIQUIDS IN BULK COMPRISING AN OUTERWALL, A THERMALLY INSULATING LAYER DISPOSED ADJACENT THE INNER SURFACEOF SAID OUTER WALL AND A DOUBLEWALLED CONTAINER DISPOSED WITHIN ANDTHERMALLY INSULATING LAYER, SAID DOUBLE-WALLED CONTAINER CONSISTING OFSPACED MAIN AND SECOND TANKS, EACH OF SAID TANKS BEING MADE OF